Recent progress in studies on the health benefits of pyrroloquinoline quinone
Pyrroloquinoline quinone (PQQ), an aromatic tricyclic o-quinone, was identified initially as a redox cofactor for bacterial dehydrogenases. Although PQQ is not biosynthesized in mammals, trace amounts of PQQ have been found in human and rat tissues because of its wide distribution in dietary sources. Importantly, nutritional studies in rodents have revealed that PQQ deficiency exhibits diverse systemic responses, including growth impairment, immune dysfunction, and abnormal reproductive performance. Although PQQ is not currently classified as a vitamin, PQQ has been implicated as an important nutrient in mammals. In recent years, PQQ has been receiving much attention owing to its physiological importance and pharmacological effects. In this article, we review the potential health benefits of PQQ with a focus on its growth-promoting activity, anti-diabetic effect, anti-oxidative action, and neuroprotective function. Additionally, we provide an update of its basic pharmacokinetics and safety information in oral ingestion.
吡咯并喹啉醌(PQQ)是一种芳香族三环氧醌，最初被鉴定为细菌脱氢酶的氧化还原辅助因子。虽然 PQQ 不是在哺乳动物中生物合成的，但由于 PQQ 在人体和大鼠组织中广泛分布，因此在人体和大鼠组织中都发现了微量的 PQQ。重要的是，啮齿类动物的营养研究表明，PQQ 缺乏症表现出多种系统反应，包括生长障碍、免疫功能障碍和异常的生殖能力。虽然 PQQ 目前还没有被归类为维生素，但 PQQ 已被认为是哺乳动物的一种重要营养素。近年来，PQQ 因其生理重要性和药理作用而受到人们的广泛关注。本文就 PQQ 的促生长作用、抗糖尿病作用、抗氧化作用和神经保护作用进行综述。此外，我们还提供了更新的基本药代动力学和口服安全信息。
Structure and redox reaction of pyrroloquinoline quinone (PQQ).
Pyrroloquinoline quinone (PQQ, Fig. 1) is an aromatic tricyclic o-quinone that serves as a redox cofactor of a number of prokaryotic dehydrogenases, such as alcohol and sugar dehydrogenases.1,2) More recently, the first eukaryotic PQQ-dependent sugar oxidoreductase has been discovered in a mushroom, the basidiomycete Coprinopsis cinerea.3) Although PQQ is not biosynthesized in mammals, trace amounts of PQQ have been found in human and rat tissues at picomolar to nanomolar levels,4) and an especially large amount has been found in human milk5) because of its presence in daily foods, including vegetables and meats.6–8) PQQ is a ubiquitous molecule that influences a multitude of physiological and biochemical processes and has been established to be beneficial for growth and stress tolerance in both bacteria and higher organisms.9,10) Most importantly, nutritional studies have revealed that PQQ deficiency in mice and rats exhibits various systemic responses, including growth impairment, compromised immune responsiveness, abnormal reproductive performance, and reduced respiratory quotient.11–13) Moreover, in 2003, Kasahara and Kato reported that PQQ could qualify as a newcomer to the B group of vitamins.14)These authors cloned a presumed mouse homolog (U26) of the yeast gene, 2–aminoadipic acid reductase(LYS2), and proposed that U26 could be involved in the metabolic degradation of dietary lysine, acting as a PQQ-dependent 2-aminoadipic 6-semialdehyde dehydrogenase, because U26 contained the putative PQQ-binding motif that is conserved among bacterial PQQ-dependent dehydrogenases.14) However, claims for a mammalian vitamin have been questioned because conclusive evidence for the existence of a mammalian PQQ-dependent enzyme is lacking.15,16) Although currently there remains controversy over whether PQQ is indeed an essential vitamin in mammals, PQQ has been discovered to have a diverse range of physiological properties that could be beneficial to human health over the last decade. The objectives of this review were to, first, present an overview of the recent insights gained on the potential health benefits of PQQ in anti-diabetic, anti-oxidative, and neuroprotective actions, and second, update its metabolism and safety information in pharmacological applications.
吡咯并喹啉醌(PQQ，图1)是一种芳香的三环氧醌，是一些原核生物的氧化还原辅助因子，如醇脱氢酶和糖脱氢酶。 1,2)最近，在一种蘑菇中发现了第一个真核 pqq 依赖性糖氧化还原酶，该真核糖氧化还原酶是一种担子菌类——椰球孢霉(Coprinopsis cinerea。 3)虽然 PQQ 在哺乳动物体内没有生物合成，但在人体和大鼠组织中已发现微量的 PQQ，其含量在微摩尔到纳摩尔水平之间; 4)由于 PQQ 存在于日常食物中，包括蔬菜和肉类中，因此在人乳中发现了大量 PQQ。 Pqq 是一种普遍存在的分子，它影响着许多生理生化过程，对细菌和高等生物的生长和抗逆性都有益处。 9,10)最重要的是，营养学研究表明，PQQ 缺乏症在小鼠和大鼠身上表现出各种全身反应，包括生长障碍、免疫应答减弱、生殖能力异常和呼吸商降低。 11-13)此外，在2003年，Kasahara 和 Kato 报告说 PQQ 可以成为 b 族维生素的新成员。 14)这些作者克隆了酵母基因2- 氨基己二酸还原酶(LYS2)的小鼠同源序列(U26) ，并提出 U26可能参与膳食赖氨酸的代谢降解，作为一个 pqq 依赖的2- 氨基己二酸6- 半醛脱氢酶，因为 U26包含在细菌 pqq 依赖的脱氢酶中保守的 pqq 结合基序。 14)然而，对哺乳动物维生素的声称受到质疑，因为缺乏哺乳动物 pqq 依赖酶存在的确凿证据。 15,16)虽然目前对于 PQQ 是否确实是哺乳动物必需的维生素仍然存在争议，但在过去十年中，PQQ 已被发现具有多种多样的生理特性，可能对人类健康有益。 本文综述了 PQQ 在抗糖尿病、抗氧化和神经保护作用方面的研究进展，并介绍了 PQQ 在药理学应用中的新陈代谢和安全信息。
I. Chemical nature of PQQ
一、 PQQ 的化学性质
PQQ (4,5-dihydro-4,5-dioxo-1H-pyrrolo[2,3-f]quinoline-2,7,9-tricarboxylic acid) is a redox active o-quinone that can be reversibly reduced to pyrroloquinoline quinol (4,5-dihydroxy-1H-pyrrolo[2,3-f]quinoline-2,7,9-tricarboxylic acid, PQQH2) through a semiquinone intermediate (Fig. 1).17) It has been demonstrated that PQQ stably acts as an efficient electron transfer catalyst from a number of organic substrates to molecular oxygen (O2), constructing quinoprotein model reactions. In the presence of ascorbate, NAD(P)H, and thiol compounds such as glutathione, PQQ undergoes a two-electron reduction to form PQQH2.18–20)Subsequently, the generated PQQH2 is oxidized back to the original quinone via the reduction of two equivalents of O2 to super oxide anion (O−2O2-), which spontaneously or enzymatically dismutates to hydrogen peroxide (H2O2).21) It is noteworthy that PQQ has the ability to catalyze continuous redox cycling so that picomole amounts of PQQ are capable of generating micromolar amounts of product.17,22) Meanwhile, PQQ can exert pro-oxidant actions by the formation of reactive oxygen species (ROS), such as O−2O2- and H2O2, via its redox cycling under certain conditions and induce oxidative protein modifications, including the oxidation of cysteinyl thiols.23) PQQ also catalyzes the oxidation of primary amines, including the ε-amino group of lysine residues in elastin and collagen, via Schiff base formation under aerobic conditions.24)Elastin oxidation by PQQ in the presence of Cu2+ results in the formation of 2-aminoadipic semialdehyde residues and eventually its derived covalent cross-links. On the other hand, PQQ easily reacts with amino acids to form imidazole derivatives, such as imidazolopyrroloquinoline quinone, in biological samples, and these derivatives are biologically active in some cases.5,8) The protonated form of PQQ shown in Fig. 1dissolves only slightly in water, and the tricarboxylic acid of PQQ dissociates in neutral pH water. Therefore, PQQ disodium salt (PQQ Na2) is generally used in various examinations because of its high solubility in waster. The atomic geometry of PQQ Na2 (commercially available as BioPQQ™, a trademark of Mitsubishi Gas Chemical Co., Inc., (Tokyo, Japan)) was resolved using single-crystal X-ray structure analysis as PQQ Na2tri-hydrate.25) PQQ Na2 has an advantage in the application to various experiments compared with free-form PQQ, because it can be handled easily owing to its water-soluble property. BioPQQ™, chemically well-characterized, was used in the following studies.
Pqq (4,5-二氢 -4,5-二氧 -1h- 吡咯并[2,3-f ]喹啉-2,7,9-三羧酸)是一种氧化还原活性的对苯二酚，可以通过半中间体(图1)可逆还原为吡咯喹啉喹啉(4,5-二羟基 -1h- 吡咯并[2,3-f ]喹啉-2,7,9-三羧酸，PQQH2)。已经证明 PQQ 作为一种高效的对苯二酚催化剂，可以从一定数量的有机物到分子氧(O2)底物，构建电子转移模型蛋白质反应。 在抗坏血酸、 NAD (p) h 和硫醇化合物如谷胱甘肽的存在下，PQQ 经过双电子还原形成 PQQH2.18-20)随后，生成的 PQQH2被氧化回醌通过两个当量的 O2还原成超氧阴离子(O2 -) ，自发或酶促反应生成过氧化氢(H2O2)。 21)值得注意的是，PQQ 具有催化连续氧化还原循环的能力，因此 PQQ 的皮克莫尔量可以产生微摩尔量的产物。 同时，PQQ 在一定条件下通过氧化还原循环形成活性氧类(ROS) ，如 O2-和 H2O2，并诱导蛋白质氧化修饰，包括半胱氨酸硫醇的氧化。 Pqq 还催化伯胺氧化，包括在弹性蛋白和胶原蛋白中赖氨酸残基的-氨基，通过席夫碱在好氧条件下的形成。 24)在 Cu2 + 存在下，PQQ 氧化弹性蛋白形成2- 氨基己二醛残基，并最终形成共价交联。 另一方面，PQQ 很容易与氨基酸反应生成咪唑衍生物，如生物样品中的咪唑吡咯喹啉醌，这些衍生物在某些情况下具有生物活性。5,8)图1所示的 PQQ 的质子化形式只在水中微溶，PQQ 的三元羧酸在中性 pH 水中解离。 因此，PQQ 二钠(PQQ Na2)因其在废水中的高溶解性而被广泛应用于各种检测中。 利用单晶 x 射线结构分析方法解决了 PQQ Na2(商品名为 BioPQQTM，商标名为三菱天然气化学公司(日本东京))的原子几何结构问题。 PQQ Na2具有水溶性好、易于处理等优点，在各种实验中的应用优于自由形态的 PQQ Na2。 生物 qqtm 具有良好的化学特性，用于以下研究。
II. Natural source of PQQ
It is well known that PQQ is distributed ubiquitously in nature and found in numerous dietary sources, including fermented soy beans (natto), tea, green peppers, parsley, kiwi fruit, and human milk.5,6) Various methods for instrumental analyses and bioassays for PQQ have been developed, but the PQQ content in foods varies in different reports because PQQ is chemically reactive and prone to form derivatives or condensation products with other nutrients.5,6,8,26,27) Kumazawa et al. have developed a method based on gas chromatography/mass spectrometry (GC/MS) with isotopic dilution for free PQQ after derivatization with phenyltrimethylammonium hydroxide.4,6,7) Using this analytical method, the levels of free PQQ in various foods, including vegetables, fruits, and teas, were determined to be in the range of 3.7–61 ng/g wet weight or ng/mL in liquid foods. Recent analyses of PQQ using a reliable liquid chromatography/electrospray-ionization tandem mass spectrometry (LC/MS/MS) method elucidated that free PQQ was present in various food samples in the range of 0.19–7.02 ng/g fresh weight or ng/mL in liquid foods.8) Based on available food composition data,4–7) it is estimated that humans consume 0.1–1.0 mg PQQ and its derivatives per day.28)
众所周知，PQQ 在自然界中广泛分布，并存在于多种饮食来源中，包括发酵大豆(纳豆)、茶叶、青椒、欧芹、猕猴桃和人乳。5,6) PQQ 的各种仪器分析和生物测定方法已经开发出来，但由于 PQQ 具有化学反应性，易于与其他营养素形成衍生物或缩合产物，因此不同的报告中食品中 PQQ 的含量也不尽相同。5,6,8,26,27) Kumazawa 等建立了苯基三甲基铵氢氧化衍生化后的游离 PQQ 的气相色谱/质谱(GC/MS)同位素稀释分析方法。4,6,7)采用该分析方法，测定了各种食品(包括蔬菜、水果和茶叶)中游离 PQQ 的含量，在湿重3.7-61 ng/g 或液体食品 ng/mL 范围内。最近使用可靠的液相色谱/电喷雾离子串联质谱法(LC/MS/MS)方法对 PQQ 进行了分析，结果显示，各种食物样本中的游离 PQQ 含量在新鲜重量0.19-7.02 ng/g 或液体食物中的 ng/mL 范围内。8)根据现有的 PQQ 食品成分数据，4-7)估计人类每天摄入0.1-1.0 mg PQQ 及其衍生物
The biosynthesis of PQQ in higher organisms has not been shown, and therefore, the major source of PQQ in these organisms, including plants and animals, is believed to be derived from microorganisms. The details of PQQ biosynthesis have not been resolved yet, but a putative pathway has been proposed on the basis of the functions of conserved genes in numerous bacteria.29) The majority of PQQ-producing bacteria contain six genes (pqqABCDEF) in an operon.10,30) These genes have been expressed in Escherichia coli, a non-PQQ producer and lead to the production of PQQ.31,32) Genetic knockout studies of each of these genes show that four of the six gene products (PqqA, PqqC, PqqD, and PqqE) are absolutely required for PQQ production.32,33) In all cases, pqqA encodes a small polypeptide, typically 20–30 amino acids in length, containing a conserved glutamate and tyrosine that serve as the backbone in PQQ biogenesis.34,35) The glutamate and tyrosine undergo post-translational modifications to form the intermediate 3a-(2-amino-2-carboxyethyl)-4,5-dioxo-4,5,6,7,8,9-hexahydroquinoline-7,9-dicarboxylic acid (AHQQ).32,34) PqqC is the most characterized and has been shown to catalyze the eight-electron oxidation and ring cyclization of AHQQ to form PQQ.35) A large number of bacteria extracellularly excrete PQQ and is indicated as micrograms per mL of broth culture.36) On the other hand, common strains of bacteria in the human intestinal tract appear to synthesize little PQQ,37,38) and hence, it seems that dietary intake is the major source of PQQ in the human body.
PQQ 在高等生物体中的生物合成尚未被证实，因此，PQQ 在这些生物体中的主要来源，包括植物和动物，被认为是来自微生物。PQQ 生物合成的细节还没有得到解决，但是已经根据许多细菌中保守基因的功能提出了一个推测的途径。29)大多数产生 pqq 的细菌在一个操纵子中包含六个基因(pqqABCDEF)。10,30)这些基因已经在非 PQQ 产生者大肠桿菌中表达，并导致 PQQ 的产生。对这些基因的基因敲除研究表明，PqqA、 PqqC、 PqqD 和 PqqE 这六种基因产物中的四种是 PQQ 生产所必需的。32,33)在所有情况下，pqqA 编码一个小的多肽，通常长度为20-30个氨基酸，包含保守的谷氨酸和酪氨酸，作为 PQQ 生物发生的骨架。34,35)谷氨酸和酪氨酸经翻译后修饰形成中间体3a-(2- 氨基 -2- 羧乙基)-4,5- 二氧 -4,5,6,7,8,9- 六氢喹啉 -7,9- 二羧酸(AHQQ)。32,34) PqqC 是最具特色的化合物，已被证明可以催化 AHQQ 的八电子氧化和环化反应生成 PQQ。35)大量细菌外排 PQQ，表示为每毫升肉汤培养物微克。36)另一方面，人体肠道中常见的细菌菌株似乎合成了少量的 PQQ，因此，饮食摄入似乎是人体中 PQQ 的主要来源。
III. Growth-promoting activity
Although no enzymes in animals have been identified that exploit PQQ as a cofactor, PQQ has been shown to be essential for normal growth and development in animals. When PQQ is omitted from a chemically defined diet fed to mice and rats, various systemic responses are observed including growth impairment, immune dysfunction, decreased reproductive performance, and reduced respiratory quotient.11–14) Oral supplementation of PQQ (above 300 ng/g diet) improves reproduction and enhances neonatal rates of growth compared with the response from diets devoid of PQQ.12) More recently, dietary supplementation of PQQ Na2 in broiler chicks has been shown to improve growth performance, carcass yield, immunity, and plasma status.39) Thus, this unique compound is characterized as an important growth factor or putative essential nutrient in animals, whereas the nutritional benefits of PQQ for human growth and development are still unknown. Although the detailed mechanism of PQQ action in animals still remains unclear, the ability to carry out continuous redox cycling suggests a role for PQQ as a cofactor, redox signaling molecule, or anti-oxidant.
虽然在动物体内还没有发现能利用 PQQ 作为辅助因子的酶，但 PQQ 已被证明对动物的正常生长和发育是必不可少的。当 PQQ 从一个化学定义的饲料喂养小鼠和大鼠，观察到各种系统反应，包括生长障碍，免疫功能障碍，生殖能力下降，呼吸商降低。11-14)口服 PQQ (300ng/g 以上)可改善生殖功能，提高新生儿生长发育率。12)近年来研究表明，肉仔鸡日粮中添加 PQQ Na2能够改善生长性能、胴体产量、免疫力和血浆状况。39)因此，这种独特的化合物被认为是动物体内重要的生长因子或假定的必需营养素，而 PQQ 对人类生长和发育的营养价值仍然是未知的。虽然 PQQ 在动物体内作用的详细机制仍不清楚，但是持续氧化还原循环的能力表明 PQQ 作为辅因子、氧化还原信号分子或抗氧化剂的作用。
In cultured human and mouse cells, PQQ also functions as a potential growth factor to promote cell proliferation when added to culture media.40–42) PQQ enhances the incorporation of [3H]-thymidine into human skin fibroblasts cultured in medium containing PQQ at concentrations as low as 3 nM. Kumazawa et al. have observed that PQQ treatment stimulates activation of extracellular signal-regulated kinase 1/2 (ERK 1/2) in c-Ha-ras transformed NIH/3T3 mouse fibroblasts, resulting in increased cell proliferation.41) ERK, one of the mitogen-activated protein kinases, activates transcription in the ras-signaling pathway and plays a pivotal role in cell proliferation and survival.43) This signal transduction by sequential phosphorylation often is initiated by the binding of peptide growth factors to receptor tyrosine kinases (RTKs). Recently, we showed that PQQ also significantly enhanced proliferation of human epithelial A431 cells at concentrations above 10 nM.42) Moreover, we found that PQQ induces the activation (tyrosine autophosphorylation) of epidermal growth factor receptor (EGFR), a RTK of the ErbB family, and its downstream target ERK 1/2 in a ligand-independent manner. The activation of the ERK pathway accompanying EGFR phosphorylation via binding of EGF plays a prominent role in the proliferation of epithelial cells. On the other hand, EGFR signaling is negatively regulated by protein tyrosine phosphatase 1B (PTP1B), which catalyzes tyrosine dephosphorylation of activated EGFR, and the inhibition of PTP1B has been reported to evoke a ligand-independent activation of EGFR.44,45) Recent findings also indicate that PTP1B activity is modulated by post-translational modification, such as oxidation and alkylation of an extremely reactive cysteine residue at the catalytic center.46) On the basis of these facts, we have elucidated that PQQ inhibits PTP1B through the oxidation of catalytic cysteinyl thiol by H2O2 produced during its redox cycling, thereby inducing the ligand-independent activation of EGFR (Fig. 2). PTP1B has a substrate-specific ability to dephosphorylate RTKs, including the insulin receptor (IR),47) insulin-like growth factor-I receptor,47) platelet-derived growth factor receptor,48) vascular endothelial growth factor receptor,49) and nerve growth factor (NGF) receptor,50)implicating the modulation of multiple growth factor-activated signaling pathways. Hence, our data suggests that inhibition of PTP1B via redox cycling by PQQ might induce a diverse range of physiological effects through potentiated RTK-mediated signaling and gene expression and exert a growth factor-like action.
PQQ 在体外培养的人和小鼠皮肤成纤维细胞中均有促进细胞增殖的潜在生长因子作用。40-42) PQQ 在含 PQQ 的低浓度培养基中促进[3H ]-胸苷掺入人皮肤成纤维细胞。在 c-Ha-ras 转化的 NIH/3T3小鼠成纤维细胞中，PQQ 刺激细胞外信号调节激酶1/2(ERK 1/2)的激活，从而导致细胞增殖增加。 ERK 是丝裂原活化蛋白激酶之一，在 ras 信号通路中激活转录，在细胞增殖和存活中起着关键作用。43)这种通过磷酸化的信号转导通常是由生长因子与酪氨酸受体激酶(RTKs)的连续结合引起的。最近，我们发现 PQQ 在10nm 以上的浓度也能显著地促进人类上皮细胞 A431的增殖。此外，我们还发现 PQQ 以一种独立于配体的方式诱导表皮生长因子受体蛋白(EGFR)及其下游靶蛋白 ERK 1/2的激活。ERK 通路的激活伴随 EGFR 的磷酸化通过结合表皮生长因子在上皮细胞的增殖中起着重要作用。另一方面，EGFR 信号通路被蛋白酪氨酸磷酸酶1 b (PTP1B)负调控，后者催化活化 EGFR 的酪氨酸脱磷酸化，而且据报道 PTP1B 的抑制作用引起了 EGFR 的非配体激活。44,45)最近的研究结果也表明 PTP1B 的活性受翻译后修饰的调节，例如在催化中心的极活性半胱氨酸残基的氧化和烷基化。46)在此基础上，我们阐明 PQQ 通过氧化还原过程中产生的 H2O2氧化催化的半胱氨酰硫醇抑制 PTP1B，从而诱导 EGFR 的非配体活化(图2)。PTP1B 具有去磷酸化 RTKs 的底物特异性能力，包括胰岛素样生长因子 i 受体(IR) ，47)胰岛素受体，47)血小板衍生生长因子受体，48)血管内皮生长因子受体，49)和神经生长因子(NGF)受体，50)涉及多种生长因子激活的信号通路的调节。因此，我们的数据表明，PQQ 通过氧化还原循环抑制 PTP1B 可能通过增强 rtk 介导的信号转导和基因表达而诱导多种生理效应，并发挥类生长因子的作用。
Fig. 2. Proposed mechanism for the ligand-independent activation of epidermal growth factor receptor (EGFR) signaling through redox cycling of pyrroloquinoline quinone (PQQ). PQQ undergoes redox cycling in the presence of reductants, such as ascorbate and glutathione, and then produces O−2O2- and H2O2. The generated H2O2 inactivates protein tyrosine phosphatase 1B (PTP1B) via the oxidation of catalytic cysteinyl thiol (Cys-215) to the corresponding sulfenic acid (–SOH), sulfinic acid (–SO2H), and sulfonic acid (–SO3H). The inhibition of PTP1B evokes the EGF-independent activation (tyrosine phosphorylation) of EGFR and subsequent activation (serine/threonine phosphorylation) of ERK 1/2.
图二。提出了通过氧化还原循环表皮生长因子受体(PQQ)非配体激活吡咯并喹啉醌(EGFR)信号通路的机制。PQQ 在还原剂如抗坏血酸和谷胱甘肽的存在下进行氧化还原循环，然后生成 O2-和 H2O2。通过催化半胱氨酸硫醇(cysteinyl thiol，Cys-215)氧化生成相应的亚砜酸(- SOH)、亚砜酸(- SO2H)和磺酸(- SO3H) ，产生的 H2O2使蛋白酪氨酸磷酸酶1B (PTP1B)失活。PTP1B 的抑制引起 EGFR 的非 egf 依赖性激活(酪氨酸磷酸化)和 ERK 1/2的丝氨酸/苏氨酸磷酸化激活(丝氨酸/苏氨酸磷酸化)。Display full size 显示全尺寸
IV. Anti-diabetic effects
Accounting for 90–95% of diabetic population, type 2 diabetes mellitus (T2DM) has increased rapidly in recent decades worldwide, and the morbidity and mortality associated with secondary complications of the disease, such as retinopathy, nephropathy, and cardiovascular disease, also have increased significantly.51)T2DM is characterized by mitochondrial disorder and chronic hyperglycemia and dyslipidemia resulting from insulin resistance of the peripheral tissues and impaired insulin secretion from the pancreas.52)Mitochondria regulate metabolic pathways through signal transduction that is essential for metabolic homeostasis and cellular function. Recent studies show that mitochondrial dysfunction of diabetic subjects is closely related to lifestyle factors, including diet, physical activity, sleep, and stress.53,54) Prolonged exercise and diet intervention can reverse, at least partly, the mitochondrial deficiency and improve the metabolic flexibility and insulin sensitivity in patients with T2DM.54,55) Recently, dietary PQQ supplementation has been revealed to enhance mitochondrial function and biogenesis and improve metabolic homeostasis in mice and rats.56–58) PQQ deficiency in young mice increases the plasma glucose level, reduces hepatic mitochondrial content by 20–30%, and suppresses mitochondrial respiration.56)Similarly, rats fed a diet deficient in PQQ exhibit elevated plasma lipid and ketone bodies owing to lower mitochondrial content and decreased energy expenditure.57) More importantly, PQQ supplementation reverses the mitochondrial alterations and metabolic impairment and significantly improves the lipid profile in diabetic UCD-T2DM rats.56,57) Mechanistically, mitochondrial biogenesis and function are stimulated by the transcriptional coactivator, peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC-1α), through activation of the nuclear respiratory factor (NRF-1 and NRF-2).59) The transcription factor cAMP-responsive element-binding protein (CREB) increases transcription of PGC-1α via a conserved CREB-binding site in the proximal promoter and is activated by exercise or fasting.60) Indeed, the exposure of mouse Hepa 1–6 hepatocytes to PQQ elevates PGC-1α promoter activity by enhancing CREB transcriptional activity and stimulating mitochondrial biogenesis (Fig. 3(A)).57,61) PQQ exposure also increases the levels of NRF-1 and NRF-2, resulting in the upregulation of the mitochondrial transcription factor A (Tfam) and mitochondrial gene expression. However, the molecular mechanism underlying the activation of CREB-PGC-1α signaling pathway by PQQ remains unclear.
占糖尿病人口90-95% 的2型糖尿病在近几十年来在世界范围内迅速增加，并且与该疾病的继发性并发症相关的发病率和死亡率，如视网膜病变、肾病和心血管疾病，也有显著增加。51)拥有属性糖尿病是由于外周组织的胰岛素抵抗和胰岛素分泌受损导致的线粒体紊乱和慢性高血糖和血脂异常。52)线粒体通过信号转导调节代谢途径，这是维持代谢平衡和细胞功能所必需的。最近的研究表明，线粒体功能障碍的糖尿病人是密切相关的生活方式因素，包括饮食，身体活动，睡眠和压力。53,54)延长运动和饮食干预至少可部分逆转2型糖尿病患者的线粒体缺陷，改善其代谢灵活性和胰岛素敏感性。54,55)近年来研究表明，PQQ 补充剂能够增强线粒体功能和生物合成，改善小鼠和大鼠的代谢稳态。56-58) PQQ 缺乏可使小鼠血糖升高，肝脏线粒体含量降低20-30% ，线粒体呼吸减弱。56)同样地，喂食缺乏 PQQ 的饮食的老鼠，由于线粒体含量降低和能量消耗减少，血浆脂质和酮体水平升高。57)更重要的是，PQQ 补充剂可逆转线粒体改变和代谢损伤，显著改善糖尿病 UCD-T2DM 大鼠的血脂水平。转录辅激活过氧化物酶体增殖物活化受体γ 辅激活因子 -1 α (pgc-1)通过激活核呼吸因子 NRF-1和 NRF-2刺激线粒体的生物发生和功能。59)转录因子 camp 反应元件结合蛋白(CREB)通过近端启动子中保守的 CREB 结合位点增加 pgc-1的转录，并被运动或禁食激活。60)实际上，小鼠 Hepa 1-6肝细胞暴露于 PQQ 通过增强 CREB 转录活性和刺激线粒体生物合成提高 pgc-1启动子活性(图3(a)(a))。57,61) PQQ 暴露还会增加 NRF-1和 NRF-2的水平，导致线粒体转录因子 a (Tfam)和线粒体基因表达上调。然而，PQQ 激活 creb-pgc-1信号通路的分子机制尚不清楚。
Fig. 3. Pyrroloquinoline quinone (PQQ)-induced activation of cAMP-responsive element-binding protein (CREB)-peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC-1α) and insulin signaling. (A) Proposed mechanism for PQQ-induced activation of CREB-PGC-1α signaling pathway. PQQ stimulates the phosphorylation and activation of CREB and enhances PGC-1α expression. Increased PGC-1α binds to and coactivates the transcriptional function of nuclear respiratory factor (NRF)-1/2 on the mitochondrial transcription factor A (Tfam) promoter. Tfam plays a crucial role in regulating mtDNA amplification and mitochondrial biogenesis. (B) Proposed mechanism for the ligand-independent activation of insulin signaling through redox cycling of PQQ. PQQ inhibits protein tyrosine phosphatase 1B (PTP1B) to oxidatively modify the catalytic cysteine through its redox cycling activity. The inhibition of PTP1B evokes the insulin-independent activation (tyrosine phosphorylation) of the insulin receptor (IR) and subsequent phosphorylation of insulin receptor substrate-1 (IRS-1) and Akt. Phosphorylated Akt stimulates translocation of glucose transporter 4 (GLUT4) to the plasma membrane, resulting in increased cellular glucose uptake.
图3。吡咯并喹啉醌(PQQ)诱导的 camp 反应元件结合蛋白(CREB)-过氧化物酶体增殖物活化受体γ 辅激活因子 -1α (pgc-1)的激活和胰岛素信号转导。(a)提出 pqq 诱导 creb-pgc-1信号通路激活的机制。PQQ 刺激 CREB 的磷酸化和激活，增强 pgc-1的表达。增加的 pgc-1结合并共激活线粒体转录因子 a (Tfam)启动子上核呼吸因子(NRF)-1/2的转录功能。Tfam 在线粒体 dna 扩增和线粒体生物发生中起重要作用。(b) PQQ 通过氧化还原循环激活胰岛素信号转导与配体无关的机制。PQQ 通过氧化还原循环活性抑制蛋白酪氨酸磷酸酶1B 氧化修饰半胱氨酸。PTP1B 的抑制引起胰岛素非依赖性激活(酪氨酸磷酸化)的胰岛素受体(IR)和随后的胰岛素受体底物1(IRS-1)和 Akt 的磷酸化。磷酸化 Akt 刺激葡萄糖转运蛋白4(GLUT4)向质膜转运，从而增加细胞对葡萄糖的摄取。Display full size 显示全尺寸
Insulin resistance, defined as a dysfunction of insulin target cells, such as hepatocytes, skeletal muscle cells, and adipocytes, to respond to the action of insulin, plays a pivotal role in the development of several metabolic abnormalities and T2DM. Mitigating insulin resistance has been considered as a primary clinical strategy to improve metabolic control in T2DM subjects. The underlying molecular pathophysiology of insulin resistance still is not well understood, but a number of lines of evidence point to a critical role of PTP1B in insulin resistance. PTP1B negatively regulates insulin signaling by catalyzing dephosphorylation of tyrosine residues in activated IRand IR substrate-1 (IRS-1).47,62) Recently, a correlation between insulin resistance states and up-regulation of PTP1B expression in adipose and muscle tissues in humans has been reported.63–65) Furthermore, transgenic overexpression of PTP1B in muscle attenuates the tyrosyl phosphorylation of IR and IRS-1, leading to insulin resistance.66) On the other hand, PTP1B-knockout mice exhibit an elevated sensitivity to insulin with increased tyrosyl phosphorylation of the IR in the liver and muscle.67,68) Thus, the inhibition of PTP1B has emerged as a potential therapeutic strategy to treat T2DM.69)More recently, we found that PQQ elicits the ligand-independent activation of insulin signaling by inhibiting cellular PTP1B and enhances glucose uptake through the translocation of glucose transporter 4 in mouse C2C12 myotubes (Fig. 3(B)).70) In addition, we demonstrated that oral administration of PQQ (20 mg·kg−1 day−1) for two weeks improved impaired glucose tolerance in type 2 diabetic KK-Ay mice. Our findings clearly suggest that PQQ can be useful in anti-diabetic treatment for T2DM subjects.
胰岛素抵抗是指肝细胞、骨骼肌细胞和脂肪细胞等胰岛素靶细胞对胰岛素作出反应的功能障碍，在几种代谢异常和 T2DM 的发生中起着关键作用。减轻胰岛素抵抗已被认为是改善 T2DM 患者代谢控制的主要临床策略。胰岛素抵抗的潜在分子病理生理学机制尚不清楚，但许多证据表明 PTP1B 在胰岛素抵抗中起着关键作用。PTP1B 通过催化活化的胰岛素受体和 IR 底物 -1(IRS-1)中酪氨酸残基的去磷酸化作用负调节胰岛素信号转导。近年来，研究发现胰岛素抵抗状态与人体脂肪和肌肉组织 PTP1B 表达上调有关。63-65)此外，转 PTP1B 基因在肌肉中的过度表达会减弱 IR 和 IRS-1的酪氨酸磷酸化，导致胰岛素抵抗。66)另一方面，ptp1b 基因敲除小鼠对胰岛素的敏感性增加，肝脏和肌肉的胰岛素抵抗磷酸化增加。67,68)因此，抑制 PTP1B 已成为治疗 T2DM 的潜在治疗策略。69)最近，我们发现 PQQ 通过抑制细胞内 PTP1B 激活胰岛素信号的配体无关激活，并通过 C2C12小鼠肌管中葡萄糖转运子4的转位增强葡萄糖的摄取(图3(b)(b))。70)此外，我们证明 PQQ 口服给药(20mg kg-1 day-1)2周可改善2型糖尿病 KK-Ay 小鼠的葡萄糖耐受不良。我们的研究结果清楚地表明 PQQ 可以用于 T2DM 患者的抗糖尿病治疗。
V. Anti-oxidative action
PQQ is reduced easily to PQQH2 by reaction with reducing agents such as NADPH, sodium borohydride, glutathione, or cysteine. A couple of in vitro studies demonstrated that the reduced form of PQQ (PQQH2) exhibits anti-oxidative capacity.71–75) The aroxyl radical-scavenging activity of PQQH2 was 7.4-fold higher than that of vitamin C, which is known as the most active water-soluble anti-oxidant.73) The singlet oxygen-quenching activity of PQQH2 was found to be 6.3-fold higher than that of vitamin C.74) Interestingly, PQQH2works as catalyst in the singlet oxygen-quenching reactions. Moreover, it has been clarified that PQQH2 may rapidly convert two molecules of α-tocopheroxyl radicals to α-tocopherol.75) These results indicate that the pro-oxidant effect of α-tocopheroxyl radicals is suppressed by the coexistence of PQQH2. The summary of the radical quenching reaction is shown in Fig. 4.
通过与还原剂如 NADPH、硼氢化钠、谷胱甘肽或半胱氨酸反应，PQQ 很容易还原成 PQQH2。71-75) pqqqh2的抗氧化活性比维生素 c 高7.4倍，被认为是最活跃的水溶性抗氧化剂。73) PQQH2的单线态氧猝灭活性比维生素 c 高6.3倍。75)这些结果表明,-生育酚氧自由基的促氧化作用被 PQQH2的共存抑制。自由基淬灭反应的总结如图4所示。
Fig. 4. The summary of radical quenching reactions. Pyrroloquinoline quinol (PQQH2) can be made from pyrroloquinoline quinone (PQQ) by reduction of NADPH, cysteine, and glutathione. Aroxyl radicals, singlet oxygen, and α-tocopheroxyl radicals are quenched by PQQH2.
图4。自由基猝灭反应综述。吡咯喹啉喹啉(PQQH2)可以由吡咯并喹啉醌(PQQ)通过还原 NADPH、半胱氨酸和谷胱甘肽合成。芳氧自由基、单线态氧和-维生素氧自由基被 PQQH2淬灭。Display full size 显示全尺寸
In experiments using cultured cells, it was reported that PQQ Na2 prevents oxidative stress-induced neuronal death.76,77) It has been shown that PQQ prevented 6-hydroxydopamine (6-OHDA)-induced cell death of the dopaminergic neuroblastoma cell line SH-SY5Y and primary rat neurons and that its preventive effect was stronger than that of vitamin C and E.76) 6-OHDA is a well-known neurotoxin that compromises mitochondria complex I, resulting in the production of ROS, such as O−2O2-, hydroxyl radicals, and H2O2. Similar results were obtained in the experiment using H2O2.77)
76,77)研究表明，PQQ 能阻止6- 羟基多巴胺(6-OHDA)诱导的多巴胺能神经母细胞瘤细胞系 SH-SY5Y 和原代大鼠神经元的细胞死亡，其预防作用强于维生素 c 和 e. 76)6-OHDA，它是一种广为人知的线粒体毒素，能破坏复合物 i，产生 ROS，如 o-2、羟基自由基和 H2O2。用 H2O2.77进行的实验也得到了类似的结果
Moreover, marked decreases in ischemia damage are found in in vivo rat models, such as cardiovascular78,79) or cerebral ischemia models.80,81) The underlying mechanisms elucidated were that PQQ acts as an anti-oxidant by scavenging O−2O2- and protects mitochondria from oxidative stress-induced damage.58)
此外，在活体大鼠模型，如心血管78,79)或脑缺血模型中，缺血损伤明显减少。80,81)其潜在机制是 PQQ 通过清除 O2- 作为一种抗氧化剂，并保护线粒体免受氧化应激引起的损伤
In humans, following a single dose of PQQ Na2 (0.2 mg/kg body weight), thiobarbituric acid reactive products (TBARS), which are measured by the malondialdehyde generated from lipid hydroperoxides, significantly decreased over the time course of the study.28) In addition, the change of TBARS values correlated significantly with the maximum plasma concentration (Cmax) for PQQ Na2. These results suggest that PQQ has a potential as an anti-oxidant.
在人体中，单次服用 PQQ Na2(0.2 mg/kg 体重)后，由脂质过氧化物产生的丙二醛测定的硫代巴比妥酸反应产物(TBARS)在研究过程中显著降低。这些结果表明 PQQ 具有抗氧化的潜力。
VI. Neuroprotection and brain function
VI.I. 第六名In vitro 体外培养 studies 研究
Neurons are susceptible to receive lethal damage from oxidative stress. This neuronal death is regarded as a cause of neurodegenerative diseases such as Alzheimer’s disease and Parkinson’s disease. In in vitrostudies, the ability of PQQ Na2 to protect human neuroblastoma SH-SY5Y cells from oxidative stress by 6-OHDA or H2O2 was tested.76,77) The cell viabilities were recovered in a dose-dependent manner by adding PQQ Na2. The inhibitory activity of PQQ Na2 was much higher than that of vitamin C or vitamin E at the concentrations tested. These results suggest that the protective effect of PQQ on 6-OHDA or H2O2-induced neurotoxicity is involved in its function as a radical scavenger, especially O−2O2-.
神经元很容易受到氧化应激的致命伤害。这种神经元的死亡被认为是神经退行性疾病如阿尔茨海默病和帕金森病的原因之一。在体外研究中，测试了 PQQ Na2对6-OHDA 或 H2O2诱导的人神经母细胞瘤 SH-SY5Y 细胞的保护作用。76,77)通过加入 PQQ Na2，细胞的活性得到了剂量依赖性的恢复。在测定的浓度范围内，PQQ Na2的抑制活性明显高于维生素 c 和维生素 e。这些结果提示 PQQ 对6-OHDA 或 h2o2所致神经毒性的保护作用可能与其作为自由基清除剂的功能有关，尤其是 O2-。
One of the interesting effects of PQQ is enhancement of NGF production. NGF, a protein composed of 118 amino acid residues, is well known as a neurotrophic factor required for the development and maintenance of peripheral sympathetic and sensory neurons. PQQ is shown to have a stimulatory effect on NGF synthesis/secretion in astroglial cells and in fibroblast cells without cytotoxicity.82,83) The precise mechanism of enhancement of NGF by PQQ is not yet clear; however, cyclooxygenase activation is supposed to be an essential process, because the induction of NGF is inhibited by cyclooxygenase inhibitor or dexamethasone.84)
PQQ 的一个有趣的作用是提高 NGF 的产生。NGF 是一种由118个氨基酸残基组成的蛋白质，是众所周知的神经营养因子，用于外周交感神经元和感觉神经元的发育和维持。PQQ 对星形胶质细胞和成纤维细胞 NGF 的合成/分泌具有刺激作用，但无细胞毒性。82,83) PQQ 增强 NGF 的确切机制尚不清楚，但环氧化酶的激活被认为是一个必要的过程，因为环氧化酶抑制剂或地塞米松可抑制 NGF 的诱导
VI.II. In vivo studies
The effects of PQQ on the learning and memory function of young rats were investigated using the Morris water maze test.85) The rats in this study were fed a diet supplemented 20 mg PQQ Na2/(kg body weight/day) for nine weeks. Rats fed a PQQ Na2-supplemented diet showed significantly better learning ability than the control rats. In addition, after receiving hyperoxia to induce oxidative stress for 48 h, rats fed PQQ Na2-supplemented diets showed better memory function than the control rats. The combination of PQQ Na2 (20 mg PQQ/(kg body weight/day)) with Coenzyme Q10 (300 mg/(kg body weight/day)) showed synergistic effects on memory function. The effect is independent of vitamin E, because the vitamin E-deficient rats did not show the effect with PQQ Na2-supplemented diets. Similar effects were observed in aged rats.86) These results suggest that PQQ is potentially effective for preventing neurodegeneration caused by oxidative stress.
85)本研究中大鼠饲喂添加20mg PQQ Na2/(kg 体重/天)的饲料9周。喂食 PQQ na2补充剂的大鼠学习能力明显优于对照组。此外，在高氧诱导氧化应激后48小时，补充 PQQ na2饮食的大鼠比对照组大鼠表现出更好的记忆功能。PQQ Na2(20mg PQQ/(kg 体重/日))与辅酶 Q10(300mg/(kg 体重/日))组合对记忆功能有协同作用。这种效果与维生素 e 无关，因为维生素 e 缺乏的大鼠在补充 PQQ na2的饮食中没有表现出这种效果。这些结果表明，PQQ 可能有效地预防由神经退行性疾病引起的氧化应激。
VI.III. Human studies
A placebo-controlled, double-blinded study using the repeatable battery for the assessment of neuropsychological status (RBANS) was conducted with the participation of 65 Japanese subjects between 50 and 70 years old who presented with self-identified forgetfulness or forgetfulness identified by a family member, colleague, or acquaintance.87) RBANS is a neuropsychological battery developed by Randolph in the United States.88) The neuropsychological battery questions allow repeated and quick evaluation of higher brain function disorders with a variety of brain disease complications. The content of the RBANS consists of five subtests of neurocognitive test paradigms [immediate memory, visuospatial/constructional, language, attention, and delayed memory]. Although the PQQ Na2 (20 mg/day) and PQQ Na2(20 mg/day) + Coenzyme Q10 (300 mg/day) groups showed significantly better total score over time, a similar improvement over time was seen in the placebo group. Differences in immediate memory scores at week eight were significantly better in the PQQ Na2 + Coenzyme Q10 group than in the placebo group. For analysis of immediate memory, subjects were stratified into two subgroups according to baseline total scores. Although no significant difference was present between groups in the high-scoring subgroup, the PQQ Na2 + Coenzyme Q10 group in the low-scoring subgroup showed a significantly better score at week 8 and week 16 than the placebo group. This finding shows that individuals with lower RBANS scores may achieve a better degree of improvement in response to PQQ Na2-supplementation than individuals with higher scores.
安慰剂对照，双盲研究，使用可重复的电池评估神经心理状态(RBANS)进行了参与65名日本受试者，年龄在50至70岁之间，谁表现出自我认定的健忘或健忘，由家庭成员，同事或熟人确定。87) RBANS 是一个神经心理电池开发的伦道夫在美国。88)神经心理电池问题允许重复和快速评估高级大脑功能障碍与各种脑部疾病的并发症。RBANS 的内容包括五种神经认知测试范式[即时记忆，视空间/构造，语言，注意和延迟记忆]。虽然 PQQ Na2(20毫克/天)和 PQQ Na2(20毫克/天) + 辅酶 Q10(300毫克/天)两组随着时间的推移显示出明显的总分数更高，但是安慰剂组随着时间的推移也有类似的改善。在第八周，PQQ Na2 + 辅酶 Q10组的即时记忆评分差异明显优于安慰剂组。在即时记忆分析方面，研究对象根据基线总分分为两个子组。虽然高分组之间没有显著差异，但低分组中 PQQ Na2 + 辅酶 Q10组在第8周和第16周的评分明显优于安慰剂组。这一发现表明，RBANS 分数较低的个体对 PQQ na2补充剂的反应可能比分数较高的个体有更好的改善程度。
The result of another human clinical study was reported very recently.89) A randomized, placebo-controlled, double-blinded study to examine the effect of PQQ Na2 on cognitive functions was conducted with 41 elderly healthy subjects. Subjects were administered orally 20 mg of PQQ Na2/day or placebo for 12 weeks. For cognitive functions, selective attention by the Stroop and reverse Stroop test90) and visual-spatial cognitive function by the laptop tablet Touch M91) were evaluated. In the Stroop test, the change of Stroop interference ratios for the PQQ Na2 group was significantly smaller than for the placebo group. In the Touch M test, the stratification analyses dividing each group into two groups showed that the score significantly increased only in the lower group of the PQQ Na2 group (initial score < 70).
89)采用随机、安慰剂对照、双盲研究方法，对41名老年健康受试者进行了 PQQ Na2对认知功能影响的研究。受试者口服20毫克 PQQ na2/天或安慰剂12周。在认知功能方面，采用 Stroop 和反向 Stroop 测验对选择性注意进行评价，采用笔记本电脑 Touch M91对视觉空间认知功能进行评价。在 Stroop 测试中，PQQ Na2组的 Stroop 干扰比的变化明显小于安慰剂组。触觉 m 检验分层分析将各组分为两组，只有 PQQ Na2组较低组得分显著增高(初始得分 < 70)。
Relating to cognitive functions, PQQ Na2 shows effects on stress, fatigue, and sleep. Seventeen adult and female subjects participated in a clinical trial using an open-label trial to evaluate the effectiveness of PQQ Na2 on stress, fatigue, quality of life, and sleep.92) The participants ingested 20 mg of PQQ Na2 daily for eight weeks. The results in the Profile of Mood States–Short Form showed that all six measures of vigor, fatigue, tension-anxiety, depression, anger-hostility, and confusion significantly improved following PQQ Na2supplementation compared with scores for those measures before supplementation of PQQ Na2. The results of the Oguri–Shirakawa–Azumi Sleep Inventory (Middle-aged and Aged version) showed significant improvement in drowsiness at awaking, sleep onset and maintenance, and sleep duration. For validation, the Pittsburgh Sleep Quality Index Japanese version also showed significant improvement in sleep-related behavior. Furthermore, the changes in these global scores were correlated with changes in the cortisol awakening response, i.e., the effects of PQQ Na2 on improvement of sleep quality are supported by a biomarker.
与认知功能相关，PQQ Na2显示了对压力、疲劳和睡眠的影响。十七名成年人和女性受试者参加了一项临床试验，使用开放标签试验来评估 PQQ Na2对压力、疲劳、生活质量和睡眠的有效性。短式心境状态调查结果显示，与补充 PQQ Na2前相比，补充 PQQ Na2后，所有6项指标的活力、疲劳、紧张-焦虑、抑郁、愤怒-敌对和混乱均有显著改善。Oguri-Shirakawa-Azumi 睡眠调查表(中老年版)的结果显示，在醒来时的睡意、睡眠开始和维持以及睡眠持续时间方面有显著的改善。为了验证，日本版的匹兹堡睡眠质量指数也显示了睡眠相关行为的显著改善。此外，这些整体评分的变化与皮质醇觉醒反应的变化相关，也就是说，PQQ Na2在改善睡眠质量方面的作用得到了生物标志物的支持。
Recently, two papers were published regarding the effect of PQQ Na2 on health benefit in humans.93,94)PQQ Na2 is helpful for the improvement of skin conditions and lipid metabolism. PQQ Na2 may be useful not only for the improvement of brain functions but also for various health benefits. The underlying mechanisms of the effects of PQQ Na2 should be elucidated further.
最近，发表了两篇关于 PQQ Na2对人体健康益处的影响的论文。93,94) PQQ Na2有助于改善皮肤状况和脂质代谢。PQQ Na2不仅可以改善大脑功能，而且对各种健康都有益处。PQQ Na2作用的潜在机制有待进一步阐明。
Since 2009, dietary supplements containing PQQ Na2 have been commercialized in the United States after the official acceptance of notification by the Food and Drug Administration, and no adverse effects have been reported. As for oral toxicity studies, a 14-day preliminary study and a 28-day repeated dose study, as acute studies, and a 13-week subchronic study were performed in rats.95) The median lethal dose was 1000–2000 mg PQQ Na2/kg body weight in male and 500–1000 mg PQQ Na2/kg body weight in female rats. In the 14-day study, high doses of PQQ Na2 resulted in increases in relative kidney weights with associated histopathology in female rats only, while a follow-up 28-day study in female animals resulted in increases in urinary protein and crystals. These findings were reversible and resolved during the recovery period. In the 13-week study, a number of clinical chemistry findings and histopathological changes were noted, which were deemed to be of no toxicological significance, as the levels were within the historical control range, were not dose-dependent, occurred at a similar frequency in control groups, or occurred only in the control group. Based on these findings, a no-observed-adverse effect level (NOAEL) of 100 mg PQQ Na2/kg body weight was determined in rats, the highest dose tested in the 13-week study. A recent study reported that the NOAEL of PQQ Na2 in rats is considered to be 400 mg PQQ Na2/kg body weight for both sex, the highest dose tested.96)
自2009年以来，在美国食品和药物管理局正式接受通知后，含有 PQQ Na2的膳食补充剂已在美国商业化，没有报告不良影响。在口服毒性研究方面，进行了为期14天的初步研究和28天的重复剂量研究，作为急性研究，并在大鼠中进行了为期13周的亚慢性研究。95)半数致死量在雄性大鼠中为1000-2000毫克 PQQ Na2/kg 体重，在雌性大鼠中为500-1000毫克 PQQ Na2/kg 体重。在为期14天的研究中，高剂量的 PQQ Na2只导致雌性大鼠肾脏相对重量的增加和相关组织病理学的增加，而对雌性大鼠进行的28天后续研究导致尿蛋白和结晶的增加。这些发现是可逆的，并在恢复期得到解决。在13周的研究中，一些临床化学发现和组织病理学改变被认为没有毒理学意义，因为水平在历史控制范围内，没有剂量依赖性，在对照组中发生在相似的频率，或只发生在对照组。基于这些发现，在大鼠体内测定了100mg PQQ Na2/kg 体重的无观察不良反应水平(NOAEL) ，这是13周研究中测定的最高剂量。最近的一项研究报道，PQQ Na2在大鼠体内的 NOAEL 被认为是400毫克 PQQ Na2/kg 体重，对两性来说，最高剂量测试
Additionally, the genotoxic potential of PQQ Na2 was evaluated in a core battery of genotoxicity tests.97) The results of the bacterial mutation assay (Ames test) were negative. Weak positive results were obtained in two separate in vitro chromosomal aberration tests at the highest dosage in Chinese hamster lung fibroblasts. Upon testing in an in vitro chromosomal aberration test in human peripheral blood lymphocytes, no genotoxic activity was noted. In the in vivo micronucleus assay in mice, PQQ Na2 at doses up to 2000 mg/kg body weight demonstrated that no genotoxic effects are expressed in vivo in bone marrow erythrocytes. From these results, PQQ was concluded to have no genotoxic activity in vivo.
此外，还用一组核心的遗传毒性试验评价了 PQQ Na2的遗传毒性。中国仓鼠肺成纤维细胞在最高剂量下进行的两次体外染色体畸变试验均获得弱阳性结果。通过对人类外周血淋巴细胞进行体外染色体畸变试验，没有发现遗传毒性活性。在小鼠体内微核试验中，PQQ Na2剂量高达2000mg/kg 体重时，骨髓红细胞无遗传毒性作用。结果表明，PQQ 在体内无遗传毒性活性。
A placebo-controlled, double-blinded safety studies in humans have been reported.98) PQQ Na2 at 20 or 60 mg/day or placebo was administered for four weeks to healthy volunteers. No adverse effects were observed in standard clinical blood tests at both dosages of PQQ Na2. In the 60 mg PQQ Na2/day dosage test, the urinary concentration of N-acetyl-β-d-glucosaminidase (NAG), which is a sensitive biomarker for renal tubular damage, did not change after the administration of PQQ Na2.
一项安慰剂对照、双盲的人体安全性研究已经被报道。98) PQQ Na2在20或60毫克/天或安慰剂给予健康的志愿者四周。两种剂量的标准临床血液检测均未观察到不良反应。在60mg PQQ Na2/d 剂量试验中，肾小管损伤的敏感生物标志物 n- 乙酰 d 氨基葡萄糖苷酶(NAG)在给药后尿浓度无明显变化。
[14C]PQQ was administered orally to mice to estimate absorption. PQQ was readily absorbed (62%) in the lower intestine and was excreted by the kidney (81%) within 24 h.99) Following a single dose of PQQ (0.2 mg PQQ Na2/kg body weight), levels of PQQ peaked in the serum after 3 h of administration at a concentration around 10 nM. The rise and clearance of PQQ Na2 in serum paralleled the change in urine.28) From these studies, the pharmacokinetic behavior of PQQ Na2 seems similar to other water-soluble vitamin B group compounds. This suggests that PQQ does not accumulate considerably in the body to produce severe damage. In rats, when PQQ Na2 was injected intraperitoneally daily for 4 days at a dose of 11.5 mg/kg body weight, functional, and morphologic changes of the kidney were observed.100) The oral administration does not give as high a blood concentration of PQQ as intraperitoneal injection, but it is necessary to monitor for excess dosage.
[14C ] PQQ 给小鼠口服，观察其吸收情况。PQQ 在小肠易于吸收(62%) ，24小时内经肾脏排出(81%)99。单剂量 PQQ (0.2 mg PQQ Na2/kg 体重)后，PQQ 在给药3h 左右达到高峰。PQQ Na2在血清中的升高和清除与尿液中的变化平行。28)从这些研究来看，PQQ Na2的药代动力学行为与其他水溶性维生素 b 类化合物相似。这表明 PQQ 不会在体内大量积累而产生严重的损害。在大鼠中，每天腹腔注射 PQQ na24天，剂量为11.5 mg/kg 体重，观察肾脏功能和形态的变化。100) PQQ 口服给药的血药浓度没有腹腔注射高，但有必要监测过量剂量。
PQQ has been shown to be a ubiquitous molecule that influences a multitude physiological and biochemical processes. In this review, we have presented recent studies supporting the role of PQQ in maintaining and improving human health. There are potential benefits from PQQ supplementation related to lipidemic and glycemic control, prevention of cardiovascular and neurodegenerative diseases, and improvement of brain functions. Recent evidence suggests that PQQ can be useful for various health benefits through different mechanisms including redox activity, radical-scavenging activity, and modulation of cell signaling pathways. According to recent observations, PQQ shows no toxicity and genotoxicity in oral administration, and thus, oral supplementation of PQQ would be a promising approach to improving health status. On the other hand, the precise molecular mechanism underlying the action of PQQ is not understood fully. The mechanistic studies that aid in defining the function of PQQ could provide further benefits for human health.
PQQ 已被证明是一种无处不在的分子，它影响着许多生理和生化过程。在本综述中，我们提出了最近的研究支持的作用，PQQ 在维护和改善人类健康。PQQ 补充剂具有降血糖、降血脂、预防心血管和神经退行性疾病以及改善脑功能的潜在作用。最近的证据表明，PQQ 可以通过包括氧化还原活性、自由基清除活性和调节细胞信号通路在内的不同机制对各种健康有益。根据最近的观察，PQQ 在口服给药中没有显示出毒性和遗传毒性，因此，口服 PQQ 补充剂将是改善健康状况的一个有希望的方法。另一方面，PQQ 作用的确切分子机制尚不完全清楚。PQQ 的机理研究有助于确定 PQQ 的功能，可为人类健康提供进一步的益处。